title: A systematic review and meta-analysis of randomized trials and prospective studies comparing covered and bare self-expandable metal stents for the treatment of malignant obstruction in the digestive tract.
abstract: BACKGROUND
  Self-expandable metal stents (SEMS) are widely used for the palliative treatment of malignant gastrointestinal obstruction. Our aim was to evaluate the evidence comparing covered and bare SEMS in the digestive tract using meta-analytical techniques.
  
  
  METHODS
  A literature search was performed using PubMed, Cochrane Library, and Embase databases for comparative studies assessing the two types of stents. The primary outcomes of interest were stent patency and patient survival; second outcomes included technical success, clinical success, tumor ingrowth, tumor overgrowth, and stent migration. A random-effects model was conducted. Pooled analysis was done separately based on the different segments of the digestive tract.
  
  
  RESULTS
  Eleven studies (8 randomized controlled trials and 3 prospective cohort studies) including a total of 1376 patients were identified. Covered SEMS were equivalent to bare SEMS in terms of technical success, clinical success, stent patency (gastroduodenal obstruction: HR =0.87, 95% CI 0.53-1.42; colorectal obstruction: HR =0.89, 95% CI 0.18-4.45; biliary obstruction: HR =0.73, 95% CI 0.41-1.32) and survival rates (esophageal obstruction: HR =1.80, 95% CI 0.73-4.44; gastroduodenal obstruction: HR =0.83, 95% CI 0.55-1.26; biliary obstruction: HR =0.99, 95% CI 0.77-1.28), although bare stents were more prone to tumor ingrowth (esophageal obstruction: RR =0.10, 95% CI 0.01-0.77; gastroduodenal obstruction: RR =0.12, 95% CI 0.03-0.55; colorectal obstruction: RR =0.21, 95% CI 0.06-0.70; biliary obstruction: RR =0.21, 95% CI 0.06-0.69), whereas covered stents had the higher risk of stent migration (gastroduodenal obstruction: RR =5.01, 95% CI 1.53-16.43; colorectal obstruction: RR =11.70, 95% CI 2.84-48.27; biliary obstruction: RR =8.11, 95% CI 1.47-44.76) and tumor overgrowth (biliary obstruction: RR =2.03, 95% CI 1.08-3.78).
  
  
  CONCLUSIONS
  Both covered and bare SEMS are comparable in efficacy for the palliative treatment of malignant obstruction in the digestive tract. Each type of the stents has its own merit and demerit relatively.
authors.affiliation: Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Yang
authors.forename: Qiong
authors.initials: Q
authors.lastname: Wu
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Ye
authors.forename: Xingshun
authors.initials: X
authors.lastname: Qi
authors.forename: Daiming
authors.initials: D
authors.lastname: Fan
mesh_terms: D006801:Humans; D007415:Intestinal Obstruction / Q000601:surgery*; D008670:Metals; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D015607:Stents
chemical_list: D008670:Metals
keywords: covered stent; digestive tract; gastrointestinal cancer; malignant obstruction; self-expandable metal stent.